1. Field of the Invention
The present invention generally relates to the forming of holes in a substrate material, such as is commonly referred to as "greensheet," for the purpose of fabricating electronic circuit components which are ultimately to be used in the manufacture of electronic devices, such as computers, or the like.
2. Description of Related Art
Numerous types of punching devices are found in the prior art. For example, U.S. Pat. No. 4,821,614 describes a punch apparatus with a single punch elements and a programmable apparatus to selectively move a carriage which supports the sheet of material being punched. Another punch apparatus with a single element is described in U.S. Pat. No. 4,872,381. IBM Technical Disclosure Bulletin, Vol. 20, No. 4, Sep. 1977, pps. 1379-1380 discusses a punch apparatus with a plurality of individually activated programmable punching elements. The substrate to be punched is supported by a movable table. IBM TDB, Vol. 26, No. 10A. Mar., 1984, pps. 5100-5102, describes a mechanical punch with a dense array of punches which are electro-mechanically affixed to a platen which is driven downward at the appropriate time causing a push rod and punch carrier to be driven down. Simultaneously, a punch is driven down, thereby piercing the substrate material IBM TDB, Vol 30, No. 6, Nov., 1989, pps. 355-358 describes a punching apparatus in which a single punch is used to form via holes in the substrate by performing punching with the substrate moving at a constant velocity (on the fly). IBM TDB, Vol. 31, No. 9, Feb., 1989, pps. 140-141, discusses a flexpunch machine which uses a punch and die assembly to produce the entire via hole pattern in the substrate. The punch and die assembly moves at a constant rate while punching the substrate.
Another conventional alternative to a single punch machine is to have an array of equally spaced punches mounted on a bar spanning the width of the substrate being punched and perpendicular to the direction of the movement of the substrate. With this arrangement, the substrate is moved in the direction of the Y-axis, and the punches are fired simultaneously as needed. If the spacing of the punches exceeds the grid size of the holes, and if the ratio of grid size to punch spacing is an integer, then the number of passes of the substrate required to complete the punching task is equal to this ratio. For each pass of the substrate, the material is indexed one grid unit along the X-axis and a discrete indexing device for incremental movement of the substrate along the X-axis is required. Further, due to physical size requirements and electric power usage, the simultaneous firing of the punches on the array requires an independent power supply for each punch. The drawbacks of this system include the power supply problems and the requirement that a discrete indexing device, movable in the X direction be provided.
None of the aforementioned references utilize sequentially controlled, multiple punches in a variable array to perforate a substrate which is being conveyed at a uniform high rate of speed. A major problem exists with punching a constantly moving substrate because the punch speed must be extremely high with respect to the substrate speed in order to avoid any distortion such as ripping, tearing, or the like. Conventional systems which punch "on the fly" must utilize an extremely large power supply in order to obtain the necessary punch speed relative to the substrate speed. Utilization of a large power supply for each punch in an array is impractical since large power supplies have correspondingly large physical size and electric power requirements which limit their use to a single punch, or a die set having plural punches affixed thereto.
Thus, it would be advantageous to have a punching apparatus capable of punching a plurality of holes into a substrate which is moving at a constant velocity. Further, it would be an improvement over conventional systems to have the ability of punching these plural holes on different centers such that electrical components having different spacing of input/output contacts can be affixed to a particular substrate.